As various electronic devices are miniaturized and weight-lightened, a photosensitive protective film capable of forming a minute opening pattern has been used in a printed circuit board (PCB), a semiconductor package substrate, a flexible printed circuit board (FPCB), and the like.
The protective film, also called a solder resist, generally requires developability, a high-resolution property, an insulating property, soldering thermal resistance, gold plating resistance, and the like. Particularly, the solder resist for a package substrate requires, in addition to such properties, for example, crack resistance to a temperature cycle test (TCT) of 55° C. to 125° C., or a highly accelerated stress test (HAST) property between fine wires.
Recently, as the solder resist, a dry film type of solder resist (DFSR, dry film solder resist) having good uniformity of film thickness, surface smoothness, and thin film formability has been drawing attention.
Using such a dry film solder resist, a process for forming the resist may be simplified, and the effect of a reduced amount of solvent discharge when forming the resist may be obtained.
Meanwhile, a semiconductor package article is configured with composite materials including a nonconductor such as an epoxy molding and a solder resist, a semiconductor such as a chip die, a conductor such as a circuit board pattern, and the like, and in order to manufacture this article, various processes involving severe thermal shock conditions should be performed.
However, since each component included in the semiconductor package article, for example, a nonconductor, a semiconductor, or a conductor has different coefficients of thermal expansion (CTE) from each other, dimensional stability may be greatly decreased, or a warpage phenomenon may occur.
The decrease in dimensional stability and the warpage phenomenon as such, when connecting a chip die and a semiconductor substrate with a solder ball or a gold wire, may cause a discrepancy in positions between a chip and a substrate, and also cracks and breakage of an article may be generated by shear stress, which may shorten the life of the article.
In addition, as the thickness of a substrate is decreased, the decrease in dimensional stability or the warpage phenomenon may be more deepened. Thus, according to a tendency of miniaturization and weight-lightening of various electronic devices, substrate materials and a solder resist having a lower coefficient of thermal expansion are more demanded.
Currently, according to a tendency of lightening, thinning, shortening, and miniaturization of electronic devices and components, the integration degree of electrical elements is being increased, and the heating value of an electrical element operating with electrical energy is being greatly increased.
Accordingly, there is a growing demand for improving heat radiation for effectively dispersing and emitting heat generated from the Inside of the electronic device.
Thus, measures for improving heat radiation for effectively dispersing and emitting heat generated from the electrical element have been variously studied.
For example, in order to improve the heat radiation property of various electrical elements, methods such as equipping a heat sink plate for conducting heat to release it outside, or of equipping a silicone rubber sheet and the like having excellent thermal conductivity, have been suggested. However, with such a heat sink plate, silicone rubber sheet, or the like, it has been difficult to firmly and closely adhere it to electrical elements, and there has been a limitation of not fully exhibiting the heat radiation property.